In situ, time-resolved X-ray diffraction study of the solid state polymerization of disulfur dinitride to polysulfur nitride

Kinetic and mechanistic aspects of the title reaction were investigated by time-resolved X-ray powder diffraction combined with Rietveld refinement The conversion of S2N2 could be followed through the whole reaction with a time resolution of one diffraction pattern per minute. Polymerization of S2N2 at 40 °C gave (SN)x in quantitative yield, albeit as a mixture of α- and β-(SN)x (about 5 and 95 %, respectively). The time dependance of the formation of both (SN)x phases is autocatalytic. The reaction could occur as single state polymerization, at least up to a monomer conversion of 75 %. Refinement of atomic coordinates for S and N up to a monomer conversion of 50 % did not give any evidence for alterations of the molecular geometry of the reactant, even though lattice parameters varied noticeably with progressing conversion.